Bestselling author Sir Terry Pratchett has been testing out a revolutionary helmet which is claimed to slow down or even reverse the effects of Alzheimer’s disease.

Science fiction writer Sir Terry, 60, who was diagnosed with early-onset Alzheimer’s in 2007, wore the strange-looking headgear once a day for three months and noticed a small improvement, his agent confirmed.

The prototype anti-dementia helmet, which must be worn for ten minutes each day, was designed by British GP Dr Gordon Dougal.